There exists a significant need for the safe handling and disposal of hazardous materials. Of concern are those areas where attempts to remove such materials could involve a further exposure of personnel due to the unwarranted spread of these potentially harmful materials. The currently accepted isolation process involves erecting protective curtain enclosures which help to confine the material within existing limits. An example is the removal of asbestos materials from habitable spaces. To date, polyethylene films have become the accepted and preferred material for construction of these isolation cells. However, a number of serious limitations exist when using polyethylene to provide the required environmental barriers.
First, polyethylene sheet materials are nonadherent and are held in place with tape. Tape failure is a common occurrence that results in collapse of the protective screen. Consequently, airborne hazardous material has free access to the unprotected surface, thus requiring additional decontamination processes.
Second, the polyethylene sheeting can be readily torn, especially when it is placed in service as a floor covering. Contact by rolling scaffolds, ladders with sharp appurtenances, hose connections, and such can easily pierce the barrier. Once penetrated, water which is used to hold down the airborne dusts, and which is bearing the hazardous material, will leak into areas behind the polyethylene.
Polyethylene sheeting is slippery, especially when wet. This presents an acute problem when polyethylene is applied in double thickness, a practice often specified to help provide more confidence in the integrity of the environmental barrier. The hazard resulting from layered sheeting is further complicated by the requirement that each crew member work in a special suit consisting of boots, rubber gloves, protective clothing, and a full-face respirator. Accidents that are directly related to the presence of the sheet polyethylene are prevalent in this industry and present a significant cost consideration. A secondary consideration is the serious loss of human productivity which this "hostile" environment presents.
The installation of polyethylene sheeting is a time consuming activity.
Polyethylene sheeting presents a smooth, slick, non-tacky surface, and harmful dusts can readily become airborne if the surface becomes dry.
A polyethylene sheet membrane has minimal contact with the substrate. Asbestos fibers which in any way evade the integrity of the environmental screen, can migrate extensively in the space between screen and the substrate which is to be protected. In some cases, the screen may actually enhance transport since movement of the polyethylene screen may actually cause a "pumping effect" where high velocity air currents encourage transport of hazardous particulate.
Because the polyethylene film is hung as a pseudo "shower curtain" screen, it is not possible for any practical negative pressure to be maintained in the work area. Such a negative pressure, which is usually maintained by an exhaust fan, is essential to controlling the escape of asbestos fibers during a removal program.
Upon removal, polyethylene sheeting has no tendency to congeal or to self compact. Thus, the burial volume is large and confinement of the freed asbestos is highly inefficient since self-embedding processes are not afforded.
Thus, there is a continuing need for a protective coating which can overcome the disadvantages of polyethylene films.